The invention relates to milling apparatus adapted to reduce a wide range of feedstock grain sizes to flour with the aid of a stationary upper millstone, provided with a central orifice for the supply of feed kernels, and a lower millstone rotated by a drive shaft. It relates, more particularly, to such apparatus wherein an initial reduction of large kernels is achieved by a primary reduction stage employing milling teeth radially protruding from the drive shaft in the region of the central orifice of the upper millstone.
Milling apparatus of this description are particularly known and used for the reduction of cereal grains and are commercially available in a wide range of sizes, including manually operated household mills and mills used in large-scale baking operations. Generally the housing in which the stationary upper millstone is located is also utilized to store and funnel the feedstock to the millstones. The feedstock is funneled from a storage chamber to the central cavity of the milling space through the aforementioned orifice in the upper millstone. The feedgrains are fed from the central cavity into the space between the millstones and the fineness of the resulting flour is controlled by the milling gap, the smaller the space between the opposing milling surfaces the finer the flours. The flour leaves the milling space at the outer periphery of the millstone and is discharged into a suitable container for further use.
In the milling of cereal grains it is paticularly important that the milling process be carefully controlled so that the feed is not excessively heated during the process. The generation of great heat can lead to the destruction of essential nutrients in the feed grain.
The milling apparatus of the prior art have a number of inherent disadvantages. One of the more serious of these disadvantages lies in their ability to accept only grains of a specified size. A cereal mill adapted to the milling of wheat, barley, rye and the like -- for example -- cannot be used for the reduction of feedstock with inherently larger kernel sizes, such as maize, soybeans, peas and the like. The larger kernels cannot be readily guided into the milling space between the stones, and -- if the stones are shaped to accept such kernels -- the large volume of the material to be mailed can lead readily to a stopping up of the milling gap. Furthermore, the milling of larger kernels in mills of the prior art is generally too rapid and leads to an unacceptable heating of the feed.
It is, therefore, a primary object of the invention to provide milling apparatus capable of accepting a wide range of feed kernel sizes.
It is a particular object of the invention to provide such milling apparatus in which the rate of size reduction of large kernels is so controlled that excessive heating or the stopping up of the milling gap is avoided.
It is a further object of the invention to provide milling apparatus of the above kind, wherein the user is not required to alter the apparatus or to provide auxiliary devices when changing from feed of one kernel size to feed of another size.
It is yet another object of the invention to provide milling apparatus adapted to the reduction to flour of a wide range of grain sizes in which the size, weight, construction cost, operating cost and maintenance compare favorably with apparatus of the prior art.
Other objects and advantages of the invention shall become apparent from the detailed description of the preferred embodiment thereof, below.